[strong] dot prototypes of strong class literals should be strong objects

test/mjsunit/strong/literals.js

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Flags: --strong-mode --allow-natives-syntax
 // Flags: --harmony-arrow-functions --harmony-rest-parameters
 // Flags: --harmony-destructuring --harmony-spread-arrays
 
 'use strict';
 
@@ skipping 292 matching lines @@
   // assertWeakClass(class D extends null {});
   assertWeakClass(class D extends C {});
   assertWeakClass(class D extends S {});
   assertWeakClass(class D extends class {} {});
 })();
 
 (function StrongClassLiterals() {
   'use strong';
   function assertStrongClass(x) {
     assertTrue(%IsStrong(x));
-    // TODO(rossberg): strongify class prototype and instance
-    // assertTrue(%IsStrong(x.prototype));
+    assertTrue(%IsStrong(x.prototype));
+    // TODO(rossberg): strongify class instance
     // assertTrue(%IsStrong(new x));
   }
   class C {};
   class D extends C {};
   class E extends Object {};
   const W = (1, eval)(() => {'use strict'; return class {}})();
   class G extends W {};
   assertStrongClass(C);
   assertStrongClass(D);
   assertStrongClass(E);
@@ skipping 18 matching lines @@
 })();
 
 (function StrongRegExpLiterals() {
   'use strong';
   function assertStrongRegExp(x) {
     // TODO(rossberg): strongify regexps
     // assertTrue(%IsStrong(x));
   }
   assertStrongRegExp(/abc/);
 })();